In identity (individual) authentication, a scheme with fingerprints has been available from long ago, but, in recent years, in place of comparison by a visual check, various automatic authentication techniques in combination an image sensor or a semiconductor sensor and image processing by a computer have been developed and widely used. Also, a method has been put into commercial use in which the pattern of a fingertip and subcutaneous veins of a palm is read by using near-infrared light and an image sensor and to extract a feature, such as a branching point, for individual authentication. However, every method is not perfect yet, and the fight against forgery continues.
For example, Patent Documents 1 and 2 disclose clear, high-resolution fingerprint sensors using a laser, but these cannot determine simulated fingerprints. By contrast, Patent Document 3 discloses a method of performing individual authentication with a vein pattern by using an ordinary light beam and also determining whether a person to be authenticated is alive by optical detection of a pulse. Although this is not fingerprint recognition, it is also possible to confirm that the person to be authenticated is alive, and therefore this is effective at preventing forgery. However, there are problems, such as those as to reliability of authentication with a vein pattern and complexity of the apparatus.
On the other hand, when a laser is radiated toward a living body, an intensity distribution of its reflected scattering light forms dynamic laser speckles (a random granular pattern) with moving scattering particles, such as blood cells. It is known that this pattern is detected by an image sensor on an imaging plane and changes with time of the pattern at each pixel are quantified and displayed in a map, thereby imaging a blood flow distribution of capillary blood vessels near the surface of the living body. And, several technologies and apparatuses using this phenomenon to measure a blood flow map under the skin or of the eyeground have been suggested by the inventors (for example, refer to Patent Documents 4 to 9).
The inventors have formed a conception of using a blood flow map for individual authentication in connection with a fingerprint pattern, diligently proceeded studies, and already suggested an individual authentication method and its means by measuring a subcutaneous blood flow. That is, the inventors have suggested the individual authentication method including: (1) a step of enlarging a laser luminous flux for radiation to the pad of the finger tip and, with light reflected from a blood vessel layer under the skin, forming an image on an image sensor by using an optical system as laser speckles; (2) a step of finding an amount representing a velocity of time changes of a light-receiving amount at each pixel of laser speckles, for example, an average time change rate or an inverse of a degree of variations of the light-receiving amount integrated according to an exposure time of the image sensor, and obtaining a blood flow map of the pad of the finger tip by taking the found numerical value as a two-dimensional map; and (3) a step of comparing and determining a finger patter appearing as a blood flow map with personal data registered in advance, and an apparatus for executing each step (refer to Patent Document 10). Also, the inventors have improved the method described above and also suggested a method and means of using a laser having a specific wavelength as illumination light for radiation to a finger tip or radiating a plurality of lasers having different wavelengths simultaneously or sequentially to the finger tip to find superposing or a plurality of blood flow velocity maps with respect to reflected light (refer to Patent Document 11).
On the other hand, conventionally, a method and apparatus of coding/encoding eyeground information from an eyeground camera shot image to form signature data and a password has also been suggested (for example, Patent Documents 12 to 15). And, the inventors have created a very powerful individual authentication technique using the laser-speckle technology described above and eyeground information to use blood flow data, which is extremely difficult to forge, such as a run of blood vessels on a retina obtained by imaging an eyeground blood flow distribution, a distribution shape of arteries and veins and, furthermore, a distribution of a choroid blood vessel layer behind the retina and used blood flow data such as blood flow changes with time, and filed a patent application (refer to Patent Document 16).    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 5-73666    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 8-16752    [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2003-331268    [Patent Document 4] Japanese Examined Patent Publication No. 5-28133    [Patent Document 5] Japanese Examined Patent Publication No. 5-28134    [Patent Document 6] Japanese Unexamined Patent Application Publication No. 4-242628    [Patent Document 7] Japanese Unexamined Patent Application Publication No. 8-112262    [Patent Document 8] Japanese Unexamined Patent Application Publication No. 2003-164431    [Patent Document 9] Japanese Unexamined Patent Application Publication No. 2003-180641    [Patent Document 10] International Publication No. 05/122896 Pamphlet    [Patent Document 11] International Publication No. 07/097129 Pamphlet    [Patent Document 12] Japanese Unexamined Patent Application Publication No. 7-213511    [Patent Document 13] Japanese Unexamined Patent Application Publication No. 11-215119    [Patent Document 14] Japanese Unexamined Patent Application Publication No. 11-149453    [Patent Document 15] Japanese Unexamined Patent Application Publication No. 2007-41831    [Patent Document 16] International Publication No. 07/142055 Pamphlet